For many years, magnetrons have been commonly used in microwave ovens to generate microwave energy for the purpose of heating food, beverages, or other items. A magnetron essentially consists of a circular chamber with multiple cylindrical cavities spaced around its rim, a cathode built into the center of the chamber, and a magnet configured to generate a magnetic field. When incorporated into a microwave system, the cathode is coupled to a direct current (DC) power supply that is configured to provide a high voltage potential to the cathode. The magnetic field and the cylindrical cavities cause electrons within the chamber to induce a resonant, high-frequency radio frequency (RF) field in the chamber, and a portion of the field may be extracted from the chamber via a probe. A waveguide coupled to the probe directs the RF energy to a load. For example, in a microwave oven, the load may be a heating chamber, the impedance of which may be affected by objects within the heating chamber.
Although magnetrons have functioned well in microwave and other applications, they are not without their disadvantages. For example, magnetrons typically require very high voltages to operate. In addition, magnetrons may be susceptible to output power degradation over extended periods of operation. Thus, the performance of systems in which magnetrons are included may degrade over time. Further, magnetrons tend to be bulky, heavy components that are sensitive to vibration, thus making them unsuitable for use in portable applications.